When your PSA and books disagree

Most MSPs bill out of their PSA and keep the books in an accounting system. ConnectWise PSA or Autotask pushing invoices into QuickBooks Online is a common setup. Once the integration is connected, it is easy to assume the two systems hold the same numbers.

They often don't. Syncs fail without anyone noticing, people edit records on one side after the transfer, and mappings set up years ago stop matching how you sell today. The PSA shows what you billed. The general ledger shows what made it across. The gap between them sits in revenue, sales tax and accounts receivable until someone goes looking.

The usual ways the two systems drift

None of these are exotic. Most MSPs that have run an integration for a few years have seen several of them.

Invoices that never sync. An invoice hits an error during export, often because of a missing customer, an inactive item or a tax setting the accounting system rejects. The invoice exists in the PSA, the client may have received it, and the books never record it. Revenue is understated and so is AR.

Edits after sync. A tech adds a forgotten hour, or someone fixes a quantity in the PSA after the invoice was already exported. Depending on how your integration handles changes, the update may not flow through. The reverse happens too: the bookkeeper adjusts an invoice in the accounting system to fix a posting problem, and the PSA keeps the old version.

Duplicates and deletions. A re-export after a partial failure can create a second copy of the same invoice. Voiding or deleting an invoice in one system does not always remove it from the other. Either way, AR shows a balance the client does not owe, or misses one they do.

Customer and tax mapping. A client gets renamed, merged or set up twice, and invoices land on the wrong customer in the books. Tax codes that don't line up between systems cause sales tax to be calculated differently on each side, which matters when you file.

Mismatched dates. An invoice dated September 30 in the PSA but exported on October 2 can land in different periods if the integration uses the export date or someone changes the date to get it through. Total revenue for the year may be right while each month is wrong.

An example of what a monthly tie-out finds

Here is an illustrative example. For September, the PSA's invoice report shows 212 invoices totaling $184,350. The accounting system shows 209 invoices for the same dates totaling $179,760. The gap is 3 invoices and $4,590.

Matching invoice numbers between the two lists explains it. Three invoices, for $2,640, $1,200 and $600, failed to sync, which accounts for $4,440. The remaining $150 is one invoice edited in the PSA after export, where an hour at $150 was added but never reached the books. $4,440 plus $150 equals $4,590, so the difference is fully explained.

The fix is straightforward once you know: resolve the sync errors, re-export the three invoices, and correct the edited one in the accounting system. Without the tie-out, the books would have been about $4,590 short on September revenue and AR, and those clients would have looked paid in full.

Three checks to run every month

These checks take less time than they sound like once you have the reports saved.

1. Tie invoice counts and totals by period. Pull an invoice list from the PSA and from the accounting system for the same date range. Compare the number of invoices, the pre-tax total, the tax total and the grand total. If both match, you are probably fine. If either is off, match invoice numbers to find which ones differ.
2. Review the sync error log. Your PSA or integration tool keeps a record of failed or pending transfers. Check it before you close the month, not after. Clear every item or write down why it is still open.
3. Reconcile AR aging. Compare the AR aging in the accounting system to open invoices in the PSA, by customer. Differences point to duplicates, deletions, payments posted on only one side or invoices on the wrong customer. The AR control account on the balance sheet should also agree with the aging report total.

Keep a short log of what each tie-out found and what you did about it. Patterns show up quickly. If the same item code fails every month, fix the mapping instead of re-exporting by hand.

It also helps to limit who can edit invoices after export, and to agree on one system as the place where invoice corrections happen. Fewer people changing records on both sides means fewer differences to chase.

This article is general information, not advice for your specific setup. Integrations and accounting systems behave differently, so adapt these checks with your accountant to fit how your systems are configured.